The UN humanitarian chief Baroness Amos described parts of Homs as “completely devastated” after being allowed to enter the battered Syrian city yesterday.

The visit by Labour life peer Valerie Amos, the Under-Secretary-General for humanitarian affairs, was the first by an independent outside observer since the Syrian military began its month-long assault of the rebellious neighbourhood of Baba Amr.

A spokeswoman for Baroness Amos's office said yesterday that the rights chief had described the district as devastated by the recent shelling and almost devoid of people.

A key stronghold of the uprising to oust authoritarian President Bashar Assad, it was wrested from rebel control on March 1.

The visit came as activists accused regime forces of trying to cover up evidence of execution-style killings and reprisal attacks following a bloody military siege on the district of Baba Amr.

The Syrian regime has kept the neighbourhood sealed off over the past six days, saying it was too dangerous for humanitarian workers to enter. But activists accused the government of engaging in a "mopping-up" operation to hide their atrocities.

"They haven't let anyone in for a week, and now they are going to let them in?" Homs activists Tarek Badrakhan told The Associated Press. "Today it's simple: They finished their crimes and hid all the proof. Now they think they can show that everything is normal."

After seizing Baba Amr from the rebels, regime forces appeared to be turning their attention to other rebel-held areas, including the northern province of Idlib near Turkey.

The shift suggested that the Syrian military is unable to launch large operations simultaneously. Witnesses said Syrian troops continued shelling northern villages in Idlib yesterday.

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